A review of low and reduced carbohydrate diets and weight loss in type 2 diabetes.

BACKGROUND: Recent evidence from randomized controlled trials of hypocaloric low carbohydrate diets in people without diabetes has shown that they promote significant weight loss over the short term. There is very little evidence for any effects of reduced carbohydrate intakes on body weight, glycaemia and cardiovascular risk in people with type 2 diabetes. METHODS: An electronic search was performed using MEDLINE (1966 to March 2007), EMBASE (1988 to March 2007) and Cochrane Central Register of Controlled Trials (1991 to March 2007) using the keywords low carbohydrate, type 2 diabetes and weight loss. Studies including subjects with type 2 diabetes who adopted a reduced carbohydrate weight loss diet were identified. Data were extracted on study design, weight loss, effects on glycaemia and cardiovascular risk and potential adverse effects. RESULTS: Six studies investigating the effects of hypocaloric reduced carbohydrate diets in people with type 2 diabetes were identified. The studies were heterogenous and most included small numbers, were short-term and provided varying amounts of carbohydrate. No studies were identified that were both low carbohydrate (<50 g day(-1)) and also designed as randomized controlled trials. All studies reported reductions in both body weight and glycated haemoglobin, with no deleterious effects on cardiovascular risk, renal function or nutritional intake. CONCLUSIONS: Conclusions are limited by study design and small numbers, but it appears that reduced carbohydrate diets are safe and effective over the short term for people with type 2 diabetes.